I haven't looked lately but I think Blindside is a mix of dismiss & Metsulfuron. Next year I will hit it early with metsulfuron maybe mixed with quicksilver.

GD,
Do you think Gallery would have any pre effect on the buttonweed seeds? I know the established plants come from tubers but the are some plants that emerge from seed. It is not on the label but was wondering?

It is often better to roll your own Blindside. I have used metsulfuron and Dismiss together. The rates used are based on the amount of metsulfuron needed to totally kill the target weed and the minimal amount of Dismiss needed to effect foliar damage. My preference is to add Quicksilver to metsulfuron, keeping Dismiss for dealing with sedges, goosegrass and crabgrass. Quicksilver also has a much more generous annual usage limit, important for those of us with long growing seasons.

Gallery will stop the seeds from germinating so prolifically. Take note that Gallery has no effect on live rhizomes or roots. If a weed is not emerging from seed, it does not work on that particular weed. Results may be equivocal if the weed is emerging from vegetative structures.